Only allow calling generated mutations from lamdba

Since Dgraph doesn’t currently support system generated fields such as @createdTime, @updatedTime for mutations, and due to the update-after-auth issue, I’m likely to need to implement all mutations as lambdas and prevent clients from calling the Dgraph generated mutations, however, it would save me a lot of time if it’s possible to use the generated mutations but only via the lambda function.

As an example, an update mutation without an “author” (if I don’t want to allow that to be updated) and created/updated fields which I instead populate in the lambda, then just invoke the Dgraph generated mutation with a complete patch.

Is it possible to make the default generated mutations only available to invoke through a lambda (or at least, not directly exposed on the public schema)?